1. Field of the Invention
The present invention relates to a liquid jet recording apparatus and, more particularly, to an X-Y plotter which effects non-impact or non-contact recording by the application of a jet of liquid marking medium to a recording medium while the amount of liquid marking medium to be jetted towards the recording medium is controlled in accordance with the recording speed.
2. Description of the Prior Art
It is known that an X-Y plotter is provided with X and Y drive units separately or simultaneously operable to move a recording head in one or both directions parallel respectively to the X and Y axes which intersect with each other. The recording head heretofore employed in the X-Y plotter utilizes a ball-point pen, a substantially cylindrical hollow pen, a pencil or any other similar recording instrument, which during recording slidingly contacts the recording medium on which information is to be recorded or drawn. It may be said that this type of X-Y plotter employs a contact recording technique in which the recording instrument contacts the recording medium to draw, for example, a line.
With the X-Y plotter employing the contact recording technique, it has been found that, because of the fact that the recording medium, the recording instrument and ink are required to be well balanced during, for example, recording or delineation of a line, the resultant line is susceptible to unclear and/or uneven reproduction. In addition, the follow-up characteristic during the high speed recording is not favorable and, therefore, the recording speed is limited to one meter per second. Moreover, when the width of a line being drawn is to be varied, the recording instrument then being used has to be replaced by another one that can draw a line of a desired width.
In the case where the recording instrument used in an X-Y plotter is in the form of a pencil, wear of the pencil that occurs as it is used to draw a line on the recording medium, is liable to cause uneven reproduction of the line and, because generally in an X-Y plotter employing the contact recording technique, the recording instrument should be mechanically moved up and down relative to the recording medium to respectively continue and interrupt the recording operation, it is not suited for high speed recording.
An X-Y plotter employing a non-impact or non-contact recording technique wherein the recording instrument does not contact the recording medium is disclosed, for example, in U.S. Pat. No. 3,689,932, patented on Sept. 5, 1972, wherein the recording head utilizes a light emitting instrument while the recording medium is in the form of a photosensitive sheet material. In this type of X-Y plotter, after the recording operation has been completed, the recording medium in the form of the photosensitive material must be developed and subsequently fixed before visual representation of information recorded on the recording medium is achieved. This means that the plotter of the above numbered patent requires facilities for the developing and fixing of the recording medium and, therefore, causes much inconvenience.
Apart from the X-Y plotter hereinabove discussed, as a method for applying liquid marking medium, for example, ink, onto the recording medium, an ink jet recording system is known which is largely employed in a facsimile recording device. This ink jet recording system is so designed that the amount of ink jetted towards the recording medium is fixed and, therefore, it cannot be directly applied as a recording instrument to an X-Y plotter which requires the velocity of movement of the recording head or instrument relative to the recording medium to vary from time to time during the recording operation. If it were applied to an X-Y plotter, the recording instrument would operate in such a manner that the line width and/or the line image density would vary with variation of the recording velocity and, therefore, recording or drawing of a line of uniform line width and density would be impossible.
Another ink jet recording system wherein a jet of ink is deflected so as to diverge from its normal path of travel towards the recording medium when the ink jet is to be interrupted is also known and, for example, disclosed in the U.S. Pat. No. 3,060,429, patented on Oct. 23, 1962. In this system, unnecessary ink that has been deflected without being applied to the recording medium should be recovered and, in addition, interruption of the ink jet can not be accurately performed.